1. Field of Invention
This invention relates to an electroluminescent display device, especially to the technology for improving the display quality of the electroluminescent display device with an electroluminescent element having an anode layer, an emissive layer and a cathode layer on an insulating substrate.
2. Description of Related Art
An electroluminescent (referred to as EL hereinafter) display devices with an EL element have been gathering attention as a display device substituting a CRT or an LCD.
FIG. 8 is a cross-sectional view of the configuration of a conventional organic EL display panel. A device glass substrate 1 has a display region, where a plurality of pixels with organic EL elements is formed, on the surface. Only one of each of the pixels of R, G, and B is shown in FIG. 8 for the sake of simplicity. Emissive layers 2R, 2C, 2B are formed on the device glass substrate 1 with a predetermined distance between themselves. Then, a cathode layer 3 extends over the entire display region of the device glass substrate 1 covering the emissive layers 2R, 2G and 2B. The cathode layer 3 is made of, for example, aluminum.
The device glass substrate 1 is attached to a sealing glass substrate 4 using a sealing resin 5 made of an epoxy resin. Although it is not shown in the figure, a desiccant layer for absorbing moisture is coated on the surface of the sealing glass substrate 4.
A driver circuit (not shown) in the figure drives the organic EL element in the organic EL panel with the configuration mentioned above. When the device is on, R, G and B lights generated from the emissive layers 2R, 2G, and 2B radiate outwards through the device glass substrate 1, which is either transparent or translucent, as shown in FIG. 8.
However, the cathode layer 3 made of aluminum reflects the light in the conventional organic EL panel, as shown in FIG. 8. The strong reflection of light by the cathode layer 3 makes the display region whitish, as the organic EL panel is viewed in a bright place, leading to the deterioration of the display contrast.